UNIVERSITY    OF    CALIFORNIA  agricultural  Experiment  Station 

College  of  agriculture  e-  j-  wickson,  director 

BERKELEY,    CALIFORNIA 


CIRCULAR  No.  58 


November,  1910 


EXPERIMENTS  WITH  PLANTS  AND  SOILS  IN 
LABORATORY,  GARDEN,  AND  FIELD 

By  FRANK  E.  EDWARDS,  M.S. 

Instructor  in  Agricultural  Chemistry,  California  Polytechnic  School, 
San  Luis  Obispo,  California 


LIST   OF   EXERCISES. 


THE  PLANT  AND  ITS  WORK. 

PAGE 

Exercise    1. — Moisture  in  the  Plant 5 

2. — Composition  of  the  Dry  Matter  of  Plants  6 

3. — Composition  of  Plant  Ash  7 

4. — Nitrogen  in  Plants  8 

5. — Transpiration  of  Water  from  the  Plant 9 

6. — Transpiration  is  through  the  Leaf 9 

7. — Circulation  in  the  Plant  9 

8. — Sunlight  and  the  Plant  10 

9. — Air  and  the  Plant  10 

10.— How  the  Plant  gets  its  Food  10 

11. — Tests  for  the  Principal  Classes  of  Plant  Compounds  11 

12. — Conditions  Necessary  for  Germination  12 

13. — Plump  and  Shrunken  Seeds  12 

14.— Seed    Testing    12 

15. — Soil  Compacting  and  Germination  13 

16. — The  Depth  of  Germination  14 

THE  SOIL  AND  ITS  RELATION  TO  PLANTS. 

17. — The  Soil  and  the  Subsoil  15 

18.— Rock  Powder 15 

19. — Plant  Growth  on  Eock  Surfaces  15 

20.— Humus  in  Soils  16 

21. — Sand,  Silt,  and  Clay  in  Soils  16 

22. — Soil-forming   Minerals   19 

23. — Local  Minerals  19 

24.— Alkali  19 

25. — Gypsum  Treatment  for  Black  Alkali  Soils  20 

26. — Local  Alkali  Lands  21 

27. — Alkali  and  Acid  Soil  Tests  21 

28. — Nitrogen   Nodules 22 

29. — Classifying  Local  Soils  According  to  Location  23 

30.— Sampling  Soils 23 

31. — Moisture  in  the  Soil  24 

32. — Collecting  Local  Soil  Samples  25 

33. — Water  holding  Capacity  of  the  Soil  25 

34. — Organic  Matter  and  Water  holding  Capacity  25 

35. — Size  of  Particles  and  Water  holding  Capacity  26 

36. — Capillarity  26 

37.— Soil   Capillarity   27 

38.— Porosity  of  the  Soil 27 

39.— Shrinkage  of  Clay  Soils 28 

40. — The  Relation  of  Color  to  Soil  Temperature  28 

41. — The  Relation  of  Evaporation  to  Soil  Temperature  28 

42. — The  Relation  of  Mulches  and  Cultivation  to  Evaporation  29 

43. — Wind  Breaks  and  Soil  Moisture  30 

44. — Fertilizers    30 

45. — The  Absorption  of  Manure  Leachings  by  the  Soil  30 

46. — Fertilizer  Field  Tests  31 

47. — Manure  and  Gypsum  Field  Tests  32 

48.— Orchard  Fertilizer  Tests  32 

49. — Crop  Rotation  32 

50.— Weeds  33 


INTRODUCTION. 

Since  the  beginning  of  my  connection  with  secondary  work  eight 
years  ago  I  have  believed  that  some  soil  study  can  with  advantage  be 
presented  to  pupils  in  the  first  year  of  the  high  school.  Among  the 
chief  reasons  for  this  early  study  are,  the  value  of  securing  their  in- 
terest in  agriculture  as  soon  as  possible;  the  fact  that  many  pupils 
attend  but  one  year  and  if  no  agriculture  be  taught  in  the  first  year 
they  receive  no  instruction  therein;  and  the  educational  value  of  de- 
termining for  themselves  by  means  of  simple  experiments  the  reasons 
for  natural  phenomena  often  seen  but  not  understood  by  them.  To 
one  who  has  received  a  college  training  in  soils  and  soil  fertility  it  is 
often  difficult  to  conceive  of  any  study  of  soils  not  preceded  by  chem- 
istry and  physics.  It  is  one  of  the  difficulties  and  misfortunes  of  a 
highly  technical  training  not  to  be  able  to  appreciate  and  to  present 
the  basic  principles  of  a  science  so  simply  as  to  be  understood  by  the 
young  mind.  Mr.  Edwards  has  been  teaching  agriculture  for  three 
years  in  the  California  Polytechnic  School  as  he  presents  it  in  these 
pages.  The  exercises  are  therefore  not  theoretical  but  a  part  of  his 
actual  work  in  presenting  the  subject  of  soils  and  elementary  agri- 
culture to  first  year  pupils.  Pupils  are  admitted  to  the  Polytechnic 
from  the  grammar  grades  and  thus  his  experience  is  fully  comparable 
with  that  of  any  teacher  of  agriculture  in  the  regular  high  school. 
Aside  from  the  experiments  dealing  with  chemical  elements  and  others 
which  may  need  to  be  demonstrated  by  the  teacher,  the  pupil  should 
perform  all  with  his  own  hands. 

It  is  hoped  that  the  teacher  may  find  the  exercises  especially  help- 
ful as  supplementary  work  in  general  science,  physical  geography,  or 
botany.  To  the  end  that  greater  progress  may  be  made  in  agricultural 
teaching  we  would  appreciate  suggestions  from  teachers  as  to  their 
experience  in  using  the  exercises. 

LEROY   ANDERSON. 


EXERCISES    IN    ELEMENTARY    AGRICULTURE 


Modern  Agriculture  is  a  many  sided  and  intricate  science,  but 
primarily  it  has  to  do  with  the  growth  of  plants.  The  object  of  this 
circular  is  to  set  forth  a  few  simple  experiments  that  will  be  of  in- 
terest to  students  in  our  Secondary  Schools,  and  create  in  them  a  de- 
sire to  understand  the  laws  that  control  the  growth  and  development 
of  the  plant — one  of  the  most  wonderful  of  all  created  things. 

THE  PLANT  AND  ITS  WORK. 

The  normal  plant  is  a  stay-at-home.  Its  roots  are  firmly  planted 
in  the  ground,  so  that  it  could  not  travel  if  it  would.  Necessity,  then, 
requires  that  it  shall  live  entirely  on  the  food  that  it  can  select  from 
its  surrounding  mediums — the  soil  which  covers  its  roots,  the  air  and 
water  which  fill  the  pore  spaces  in  the  soil,  and  the  air  which  envelops 
its  stem  and  branches.  Exercise  one  and  two  will  show  the  constitu- 
ents of  the  plant — the  materials  gathered  from  these  three  sources. 

Exercise  1. — Moisture  in  the    Plant. 

Apparatus :  A  small  pan  or  a  can  lid  with  a  capacity  of  100  c.c. 
to  150  c.c,  a  balance  sensitive  to  10  milligrams,  weights  for  balance, 
sheet  iron  drying  oven,  thermometer,  gas  burner  or  other  source  of 
heat. 

Dry  the  pan  and  weigh  it  carefully.  Nearly  fill  it  with  the  finely 
cut  stem  and  leaves  of  a  fresh  plant  that  is  growing  vigorously.  Weigh 
again.  Record  all  weights.  Get  the  weight  of  the  plant  material  by 
difference.  Place  the  pan  in  the  oven  and  keep  the  temperature  at 
100°  to  105°  C.  for  five  or  six  hours.  Cool  and  weigh.  Heat  in  the 
oven  again  for  an  hour  and  again  cool  and  weigh.  If  the  weight  is 
constant  the  material  is  dry.  If  there  is  an  appreciable  difference 
shown  by  the  two  weighings,  repeat  the  heating,  cooling  and  weigh- 
ing till  a  constant  weight  is  shown.  The  total  loss  in  weight  repre- 
sents the  amount  of  water  held  mechanically  by  the  plant.  Calculate 
the  amount  in  percent  of  the  original  weight  of  the  plant  material. 
Tell  some  ways  in  which  this  mechanically  held  water  is  of  use  to  the 
plant.  Our  ordinary  growing  plants  hold  from  75%  to  95%  of  water 
in  this  way.     Save  the  dry  material  for  Exercises  two  and  four. 


Exercise  2. — Composition  of  the  Dry  Matter  of  Plants. 

Apparatus :  Porcelain  crucible  No.  0,  250  c.c.  flask,  gas  or  alcohol 
burner,  wire  triangle,  iron  tripod  or  ring  stand. 

Nearly  fill  the  crucible  with  dried  plant  material  and  heat  it  over 
the  burner  till  the  substance  begins  to  blaze.  Remove  the  burner  and 
quickly  hold  over  the  blazing  material  the  flask,  nearly  full  of  cold 
water  and  clean  and  dry  on  the  outside.  Note  the  condensation  of 
water  on  the  cold  surface  of  the  flask.  As  the  material  used  was  dry, 
this  water  must  have  been  produced  by  the  breaking  up  of  the  plant 
tissues.  It  consists  of  Oxygen  and  Hydrogen,  two  elements  of  plant 
composition.  This,  as  well  as  the  mechanically  held  water  was  de- 
rived from  the  soil  water,  having  risen  through  the  roots.  Remove 
the  flask  and  observe  the  charred  mass  remaining  in  the  crucible.  It 
is  principally  carbon  and  is  derived  from  the  air.  Continue  to  heat 
the  crucible  till  there  remains  only  a  light,  gray  colored  ash.  These 
ashes  show  the  part  of  the  plant  that  is  derived  from  the  soil.  How 
does  it  compare  in  amount  to  the  part  derived  from  the  water  and  air 
(the  part  that  has  burned  away)  ?  Save  the  plant  ash  for  Exercise 
three. 

The  average  plant  derives  about  9.0%  of  its  weight  from  the  air, 
89.5%  from  the  water  and  1.5%  from  the  soil.  The  air  always  sup- 
plies its  portion  of  the  plant  food  without  the  assistance  of  the  farmer ; 
our  California  soils  are  generally  quite  fertile  and  with  proper  meth- 
ods of  cultivation  will  usually  yield  their  part  of  the  food;  but  to 
supply  the  large  amount  of  water  that  the  plant  soil  requires,  offers 
a  problem  that  is  becoming  very  serious,  and  one  to  which  we  are 
prone  not  to  give  proper  consideration. 

Chemical  Elements  in  Plants. 

Chemists  have  studied  the  matter  that  makes  up  this  world  of  ours 
until  they  have  reduced  it  to  about  eighty  simple  substances  which 
they  term  elements.  More  than  half  of  these  elements  are  rare  and 
are  of  minor  importance  to  agriculture.  Only  ten  elements  seem  to 
be  necessary  for  plant  growth.  They  are :  potassium,  calcium,  mag- 
nesium, iron,  sulphur,  phosphorus,  carbon,  oxygen,  hydrogen  and 
nitrogen.  Carbon  is  derived  from  the  carbon  dioxide  in  the  air; 
hydrogen  and  oxygen  from  the  water  taken  into  the  plant ;  and  the 
other  seven  come  from  the  soil.  Of  the  soil  elements  potassium,  phos- 
phorus and  nitrogen,  and  sometimes  calcium,  are  used  by  the  plant 
to  such  an  extent  that  it  becomes  necessary  to  supplement  what  is  in 
the  soil  with  fertilizers.     Besides  the  elements  named,  sodium,  silicon 


and  chlorine  are  found  in  all  plants,  but  according  to  the  best  authori- 
ties they  seem  to  serve  no  useful  purpose.  Another  element  which  is 
of  importance  to  agriculture  is  aluminum.  It  is  not  a  plant  food,  but 
as  one  of  the  principal  constituents  of  clays  it  is  a  very  important 
factor  in  plant  growth.  The  clay  in  a  soil  serves  to  hold  and  give  to 
the  plant  some  of  its  food  that  would  otherwise  be  washed  away.  None 
of  the  above  named  elements  are  found  in  the  plant  or  in  the  soil  in 
the  simple  or  elemental  form,  but  are  always  combind  with  other 
elements  to  form  chemical  compounds. 

If  the  students  have  not  had  experience  in  making  chemical  tests 
the  teacher  may  make  the  following  tests  for  the  class. 


Exercise  3. — Composition  of  Plant  Ash. 

Apparatus :  Evaporating  dish,  funnel,  filters,  test  tubes,  three 
inches  of  platinum  wire  (fine  iron  wire  may  be  used),  cobalt  blue 
glass  (or  a  blue  glass  bottle),  glass  stirring  rod. 

Place  in  an  evaporating  dish  about  one-half  gram  of  the  plant  ash 
left  from  exercise  two.  Add  to  it  5  c.c.  each  of  distilled  water  and 
strong  hydrochloric  acid,  and  a  few  drops  of  strong  nitric  acid.  A 
rapid  frothing,  or  effervescence,  when  the  acid  is  added,  proves  that 
carbon  is  a  constituent  of  the  ash.  Heat  the  mixture  to  boiling  and 
evaporate  it  nearly  to  dryness.  Add  10  c.c.  distilled  water  and  stir 
well  with  a  glass  rod.  The  small  amount  of  white  insoluble  matter 
contains  the  silicon  of  the  plant  ash.  Filter  and  wash  the  residue  on 
the  filter  with  a  little  distilled  water  and  add  the  washings  to  the 
filtrate.  To  this  add  ammonia  with  constant  stirring  till  the  solu- 
tion smells  strongly  of  the  ammonia,  and  heat  to  boiling.  Filter  and 
wash  the  residue  as  above  and  save  the  filtrate  and  washings  to  test 
for  calcium.  To  the  residue  on  the  filter  add  a  few  drops  of  hydro- 
chloric acid,  and  to  the  liquid  that  passes  through  add  a  drop  of 
potassium  sulpho-cyanate  solution.  A  red  color  proves  iron.  Heat 
to  boiling  the  filtrate  saved  to  test  for  calcium  and  add  5  c.c.  am- 
monium oxalate  solution.  A  milky  white  precipitate  shows  calcium 
in  the  ash.  Filter  and  wash  as  above  and  divide  the  filtrate  and  wash- 
ings into  two  parts.  To  one  part  add  slowly  drop  by  drop  5  c.c.  sodium 
phosphate  solution.  Add  5  c.c.  strong  ammonia.  A  white  precipitate 
forming  on  standing  (immediately  if  there  is  much  magnesium) 
proves  magnesium  a  constituent  of  the  plant  ash.  Place  the  remain- 
ing half  of  the  above  solution  in  an  evaporating  dish.  Evaporate  to 
dryness  and  heat  to  a  dull  redness  if  possible,  or  till  white  vapors  no 


8 

longer  come  off.  Cool  and  add  to  the  residue  a  drop  or  two  of  hydro- 
chloric acid.  Heat  a  platinum  wire  in  a  colorless  gas  flame  till  it 
gives  no  yellow  color  to  the  flame.  Dip  the  wire  into  the  residue  and 
again  heat  it  in  the  colorless  flame.  A  bright  yellow  color  imparted 
to  the  flame  proves  sodium.  Repeat  the  above  platinum  wire  test  ob- 
serving it  through  a  dark  blue  glass  or  a  blue  bottle  that  will  shut 
out  the  yellow  color.  A  violet  color,  visible  only  through  the  blue 
glass,  proves  potassium  to  be  in  the  ash. 

To  a  fresh  portion  of  about  half  a  gram  of  plant  ash  add  5  c.c. 
each  of  distilled  water  and  strong  nitric  acid.  Heat  to  boiling,  add 
10  c.c.  more  of  distilled  water  and  filter.  Divide  the  filtrate  into  three 
parts.  To  one  part  add  2  c.c.  silver  nitrate  solution.  A  white  pre- 
cipitate, or  a  milkiness  imparted  to  the  solution,  proves  chlorine  in  the 
ash.  To  the  second  portion  add  2  c.c.  barium  chloride  solution.  A 
white  precipitate  or  a  milkiness  proves  sulphur.  To  the  last  portion 
of  the  filtrate  add  5  c.c.  ammonium  molybdate  solution  and  heat  to 
blood  temperature.  Let  stand  for  a  while  and  a  yellow  precipitate 
will  prove  phosphorus  in  the  ash. 

Exercise  4. — Nitrogen  in  Plants. 

Apparatus :  Hard  glass  test  tube,  and  one  hole  rubber  stopper  to 
fit,  glass  and  rubber  tubing  for  delivery  tube,  litmus  paper,  burner, 
test  tube. 

Mix  a  gram  of  the  dried  plant  material  from  exercise  one  with  ten 
grams  of  soda-lime.  Place  the  mixture  in  a  hard  glass  test  tube  about 
an  inch  in  diameter.  Close  the  tube  with  a  one-hole  rubber  stopper 
connected  with  a  delivery  tube  that  dips  into  a  test  tube  of  distilled 
water  in  which  is  placed  a  few  small  pieces  of  red  litmus  paper.  Ap- 
ply strong  heat  to  the  hard  glass  tube  for  five  minutes  or  more.  Am- 
monia is  formed  from  the  plant  nitrogen  and  this  passing  over  dis- 
solves in  the  water.  If  the  litmus  paper  turns  blue  it  is  a  proof  that 
the  plant  contained  nitrogen. 

Water  needed  for  Plant  Growth. 

Exercise  one  and  two  have  shown  us  that  a  very  large  amount  of 
water  enters  into  the  composition  of  the  plant.  Every  ton  of  growing 
plants  contains  nearly  1,800  pounds  of  water,  and  the  elements  of 
water  that  have  entered  chemically  into  the  plant  tissue.  But  these 
figures  represent  only  a  small  part  of  the  water  necessary  for  the 
growth  and  development  of  that  amount  of  plant  material. 


Exercise  5. — Transpiration  of  Water  From  the  Plant.     (Field 

Exercise.) 

Apparatus :  A  sheet  of  oiled  paper,  a  half  gallon  fruit  jar. 

In  the  field  or  garden  select  a  growing  plant  about  six  inches 
high.  Remove  all  surrounding  vegetation  within  a  foot,  and  smooth 
the  ground  around  the  base  of  the  plant.  Carefully  arrange  a  sheet  of 
oiled  paper,  or  other  waterproof  fabric,  about  the  stem  of  the  plant  to 
prevent  any  evaporation  from  the  soil.  Invert  over  the  plant  a  clean, 
dry,  wide  mouthed  half  gallon  fruit  jar.  If  the  sun  is  shining  you 
will  within  a  few  minutes  notice  that  the  glass  becomes  blurred  and 
that  something  is  collecting  on  the  inner  surface.  What  is  it?  How 
did  it  get  there?  This  experiment  may  be  performed  in  the  labora- 
tory with  a  potted  plant  if  the  weather  is  not  suited  to  a  field  ex- 
periment. 

Experimenters  have  proven  that  the  weight  of  water  transpired  in 
a  season  is  from  fifty  to  seventy  times  the  weight  of  the  growing  crop. 
Besides  the  water  used  by  and  passing  through  the  plants,  a  very 
large  amount  is  lost  by  drainage  and  evaporation  from  the  soil.  From 
the  above  figures  we  can  begin  to  realize  the  importance  of  water  to 
Agriculture. 

Exercise  6. — Transpiration  is  Through  the  Leaf. 

Apparatus :  Three  wide  mouth  bottles,  125  c.c.  capacity,  of  the 
same  size  and  shape. 

Obtain  several  long  stemmed  leaves  of  the  same  size  and  kind. 
Place  the  stem  ends  of  a  few  of  the  leaves  into  one  of  the  bottles  and 
the  leaf  ends  of  a  like  number  of  leaves  into  another,  leaving  the 
stems  sticking  out.  Let  the  third  bottle  serve  for  comparison.  Fill 
all  the  bottles  to  exactly  the  same  height  and  place  them  side  by  side 
in  a  warm  place.  After  about  three  hours  note  the  difference  in  the 
water  level  in  the  three  bottles.  If  there  is  no  very  perceptible  dif- 
ference, wait  until  the  next  day  and  observe  again.  Explain.  Why 
does  a  field  covered  with  growing  vegetation  loose  more  water  by 
evaporation  than  a  fallow  field,  other  conditions  being  alike? 

Exercise  7. — Circulation  in  the  Plant. 

Apparatus:  A  small  wide  mouth  bottle. 

Nearly  fill  a  small  wide  mouth  bottle  or  flask  with  water  which 
has  been  colored  a  bright  red  with  eosin  red,  or  with  red  ink.  Care- 
fully pull  out  by  the  roots  a  young  plant  with  light  colored  leaves. 


10 

Shake  it  gently  to  remove  any  adhering  soil  and  place  the  roots  into 
the  bottle  of  red  solution.  Set  it  aside  for  a  day  and  then  examine 
the  plant.  Explain  what  has  taken  place.  How  does  the  plant  get 
its  water?  Plant  food  in  the  soil  to  be  available  for  plant  use  must 
be  soluble  in  water.    How  does  it  get  into  the  plant? 

Exercise  8. — Sunlight  and  the  Plant.      (Field  Exercise.) 

Apparatus :  A  tight  wooden  box. 

In  the  field  or  garden  select  two  like  plants  growing  a  few  feet 
apart.  Invert  over  one  a  tight  wooden  box,  large  enough  to  give  room 
for  the  plant  to  grow,  being  careful  to  block  it  up  a  little  from  the 
ground  to  allow  circulation  of  the  air.  Every  two  or  three  days  ob- 
serve and  compare  the  two  plants  until  a  decided  difference  in  the 
color  of  the  leaves  is  shown.  How  do  you  account  for  the  difference? 
In  the  pasture  turn  over  a  board  or  stick  of  wood  that  has  lain  on  the 
grass  for  a  long  time.  Plow  does  the  grass  look  under  it?  Is  light 
necessary  for  plant  growth? 

Exercise  9. — Air  and  the  Plant. 

Apparatus:  Two  screw  top  half-gallon  jars. 

Place  about  three  inches  of  good  soil  in  each  of  two  screw  top  half- 
gallon  jars.  Plant  three  or  four  seeds  of  corn  or  beans  in  each.  Place 
the  jars  in  a  suitable  place  for  growth,  water  the  soil  well  and  leave 
them,  giving  water  from  time  to  time  if  necessary.  "When  the  plants 
are  about  two  inches  high  water  both  jars  well  again  and  screw  the 
top  onto  one  until  it  is  air  tight.  Leave  the  other  uncovered,  keeping 
other  conditions  the  same  for  both  jars.  Examine  from  time  to  time 
for  a  few  days.    Explain  what  has  happened. 

Exercise  10. — How  the  Plant  Gets  Its  Food. 
Apparatus :  Small  pocket  lens. 

(a)  Very  carefully  remove  from  loose,  well  cultivated  soil  several 
small  plants.  Examine  the  roots  for  hair-like  growth.  These  are 
called  root  hairs.  They  are  not  roots  but  are  hair-like  cells  that  reach 
out  through  the  soil  and  take  up  most  of  the  plant  food  that  enters 
from  the  soil,  drinking  it  in  with  the  water. 

(b)  Examine  the  under  side  of  several  different  kinds  of  leaves, 
using  a  pocket  magnifying  glass.  Notice  the  occasional  small,  mouth- 
like openings.  These  are  the  breathing  pores  of  the  plant,  and  are 
called  stomata  (singular,  stoma).     The  air  is  drawn  in  through  these 


11 

pores  and  enters  the  active  part  of  the  leaf,  which  with  the  aid  of 
sunshine,  extracts  the  carbon  from  the  carbondioxide  causing  it  to 
unite  with  water  and  other  foods  brought  up  from  the  soil.  In  this 
manner  starch  is  made  in  this  little  laboratory  of  the  plant,  the  leaf, 
and  from  starch  other  plant  compounds  are  formed. 


Exercise  11. — Tests  for  the  Principal  Classes  of  Plant  Compounds. 

Apparatus:  Knife,  test  tube,  small  wide  mouth  bottle  with  tight 
stopper,  funnel,  filter,  evaporating  dish. 

(a)  Starches. — Make  a  few  scratches  in  the  surface  of  a  growing 
leaf,  make  sections  of  a  potato,  a  grain  of  corn  and  a  bean.  To  these 
cut  surfaces  apply  very  small  drops  of  dilute  iodine  solution.  The 
purplish  blue  color  produced  is  due  to  the  action  of  the  iodine  on  the 
starch  that  they  contain.  If  any  of  these  tests  fail  to  give  marked 
results,  boil  the  substance  to  be  tested  in  water,  having  first  crushed 
it.  Cool  the  water  solution  and  test  it  with  a  drop  of  the  iodine.  A 
deep  blue  color  should  result. 

(&)  Proteids.  (The  nitrogenous  plant  compounds).  Cut  cross  sec- 
tions of  corn,  beans  or  peas  and  carefully  touch  the  cuts  with  a  glass 
rod  that  has  just  been  dipped  in  strong  nitric  acid.  Note  the  yellow 
color  which  will  become  more  intensely  yellow  if  the  strong  ammonia 
is  applied  to  the  acid  spots.  This  coloration  is  due  to  the  action  of 
the  reagents  on  the  proteids  in  the  seeds. 

(c)  Fats. — Grind  a  tablespoonful  of  oats,  corn  or  castor  beans,  or 
half  as  much  flax  seed.  Place  it  in  a  wide  mouth  bottle  and  in  a  cool 
place  away  from  all  flames.  Pour  over  it  15  c.c.  of  ether,  stopper 
tightly,  and  shake  occasionally  for  a  half  hour.  Drain  the  liquid 
through  a  coarse  filter  into  a  clean  evaporating  dish,  and  let  the  ether 
evaporate  spontaneously  in  the  open  air.  The  oily  residue  is  the  plant 
fat  (oil). 

Seeds, 

The  life  object  of  the  plant  is  to  reproduce  its  kind.  In 
most  farm  crops  this  is  done  through  the  seeds.  The  parent 
plant  surrenders  its  life  in  order  that  every  bit  of  energy  that  it  has 
stored  up  may  be  transferred  to  its  seeds,  the  embryos  of  the  next 
generation  of  plants.  We  will  now  consider  the  conditions  necessary 
to  transform  the  inert  seed  into  the  active,  growing  plant.  This  pro- 
cess is  called  germination. 


12 


Exercise  12. — Conditions  Necessary  for  Germination. 

Apparatus:  Six  tomato  cans. 

Number  the  cans  from  one  to  six.  Fill  numbers  one,  four  and  six 
with  rich,  moist  loamy  soil.  Fill  number  three  with  the  same  kind  of 
soil,  having  first  thoroughly  air-dried  it.  Leave  numbers  two  and  five 
without  soil.  Plant  in  each  of  the  soil-filled  cans  six  seeds  of  peas,  or 
beans,  to  a  depth  of  one  inch,  and  press  the  soil  firmly  around  the 
seed.  Place  the  same  number  of  seed  loose  in  numbers  two  and  five. 
Numbers  one,  two,  four  and  six  are  to  be  kept  moist  throughout  the 
experiment.  Fill  number  five  with  water,  that  has  been  previously 
boiled  and  cooled,  to  keep  out  air.  Place  numbers  one,  two,  three,  and 
five  in  a  warm,  light  place.  Place  number  six  in  a  warm  place  but 
cover  it  with  dark  cloth  or  paper  to  exclude  the  light.  Keep  number 
three  in  a  refrigerator  or  ice  box  so  that  the  temperature  may  be 
maintained  near  the  freezing  point.  Examine  the  cans  after  two  or 
three  days,  and  then  every  day  until  you  can  answer  the  following: 
Which  of  these  conditions ;  soil,  moisture,  warmth,  air,  light,  are  nec- 
essary for  the  germination  of  seeds?  Seeds  contain  a  very  small 
amount  of  air.  The  water  may  also  contain  a  small  amount  of  air. 
Take  this  into  account  in  answering  the  questions. 

Exercise  13. — Plump  and  Shrunken  Seeds. 

Apparatus:  A  shallow  box  approximately  a  foot  wide  and  two 
feet  long. 

From  a  sample  of  seed  wheat  select  100  plump  grains  and  also 
100  grains  that  are  much  shrunken.  Fill  the  box  with  a  good  rich 
loamy  soil.  Divide  the  box  in  the  middle  and  plant  the  plump  seeds 
in  one  end  and  the  shrunken  in  the  other.  Keep  the  soil  moist  and 
warm.  Examine  the  young  plants  from  time  to  time  as  they  ger- 
minate and  grow.  How  many  plants  did  you  get  from  the  plump 
seeds?  How  many  from  the  shrunken?  Let  the  plants  continue  to 
grow  till  they  are  nearly  mature.  Can  you  detect  any  difference  in 
the  hardiness  of  the  plants  and  the  amount  of  plant  material  produced 
by  the  two  grades  of  seed? 

Exercise  14. — Seed  Testing. 

Apparatus:  Balance  and  weights,  blotting  paper,  granite  ware 
plate. 

(a)  Purity. — Thoroughly  mix  the  sample  to  be  tested  and  weigh 
out  100  grams  of  the  seed  taken  fairly  from  the  whole  sample.    Care- 


13 

fully  separate  the  weighed  sample  into  the  following  parts:  (1) 
Pure  seed.  (2)  Weed  seeds.  (3)  Inert  matter-dirt,  broken  seed, 
straw,  etc.  Weigh  each  part.  The  weight  of  each  part  in  grams  is 
equivalent  to  its  percent  in  the  original  sample.  The  percentage  of 
pure  seed  is  called  the  purity  of  the  sample.  Examine  the  weed  seed 
to  see  if  you  can  recognize  any  of  them.  Try  to  learn  if  any  of  them 
are  the  seeds  of  pests.  Even  a  few  pest  seeds  would  be  enough  to 
condemn  the  sample. 

(&)  Germination  Test. — Fit  a  piece  of  blotting  paper  to  the  inside 
of  a  granite  ware  pie  pan,  or  an  ordinary  soup  plate,  moisten  it  with 
all  the  wrater  that  it  can  absorb.  Count  out  100  of  the  pure  seeds  ob- 
tained in  (a).  Distribute  them  well  over  the  blotter  in  the  plate  and 
cover  them  with  another  moistened  blotter.  Invert  over  all  a  plate 
of  the  same  size  as  the  first,  and  place  in  a  warm  place.  After  about 
two  days  begin  to  examine  the  test  occasionally.  Each  time  remove 
the  seeds  that  have  sprouted  and  count  and  record  their  number. 
When  all  have  sprouted  that  will,  the  total  number  of  seeds  germin- 
ated represents  the  percent  of  germination.  The  percent  of  germina- 
tion multiplied  by  the  percent  of  purity  gives  the  percent  of  good  seed 
in  the  sample. 

In  this  manner  test  samples  of  alfalfa,  wheat,  beans,  or  other  seeds 
that  are  used  in  your  locality.  Seeds  shipped  from  other  localities  are 
liable  to  carry  noxious  weeds  that  will  be  introduced  and  prove  a 
pest  in  your  community.  Examine  the  fields  of  the  locality.  How 
many  pest  weeds  do  you  find?  Make  inquiry  from  the  farmers  to 
learn  which  are  native  and  which  are  imported. 


Exercise  15. — The  Effect  that  Packing  the  Soil  Has  on  Seed  Ger- 
mination.    (Field  Exercise.) 

Apparatus:    Garden  tools. 

Prepare  a  plat  about  six  feet  square  in  a  rich,  moist  garden.  Plant 
across  it  four  rows  of  radish  or  other  garden  seed.  Carefully  firm 
the  soil  over  two  of  the  rows  by  treading  on  them,  heel  to  toe,  for  the 
full  length.  Leave  the  other  two  rows  covered  loosely.  Watch  the 
plat  from  day  to  day  to  see  which  rows  first  appear.  Where  the  soil 
is  compressed  it  is  giving  up  its  moisture  over  the  entire  surface  of 
the  seed.  The  loose  soil  does  not  touch  nearly  the  whole  surface  of 
the  seed.  How  does  moisture  effect  seeds  (Ex.  12)  ?  Do  not  water 
the  plat  while  the  test  is  being  carried  on. 


14 


Exercise  16. — Depth  of  Germination. 

Apparatus:  Three  half-gallon  fruit  jars,  three  pint  fruit  jars. 

(a)  Large  Seeds. — Place  about  V/2  inches  of  good  moist  soil  in  the 
bottom  of  each  of  the  half-gallon  jars.  Plant  one  with  peas,  one  with 
beans,  and  one  with  corn,  as  follows :  Plant  two  seeds  near  together 
against  the  wall  of  the  jar  and  on  the  surface  of  the  soil.  Add  an 
inch  of  soil,  press  it  down  gently  and  after  turning  the  jar  slightly 
to  one  side  plant  two  more  seeds  so  that  they  will  not  be  directly  over 
those  already  planted.  Continue  to  add  soil  and  plant  seeds  every 
inch  up  the  side  of  the  jar  till  near  the  top.  Wrap  each  jar  in  dark 
cloth  or  paper  to  exclude  the  light,  and  set  in  a  warm  place.  From 
day  to  day  remove  the  wrapping  from  the  jars  and  note  the  growth, 
recovering  them  immediately.  This  exercise  should  give  some  idea  of 
the  power  of  different  kinds  of  seeds  to  force  their  plantlets  up 
through  the  soil.  Note  the  depth  of  the  lowest  seed  in  each  jar  that 
is  able  to  penetrate  to  the  surface. 

(b)  Small  seeds. — Repeat  (a)  using  pint  jars  and  planting  the 
lowest  seeds  about  an  inch  from  the  bottoms.  Use  small  seeds,  such 
as  radish,  alfalfa,  clover. 

How  do  the  depths  of  germination  with  large  and  small  seeds 
compare?  Give  a  reason  for  this.  Oil  producing  seeds  contain  much 
more  food  in  proportion  to  their  size  than  do  the  starchy  seeds. 


THE  SOIL  AND  ITS  RELATION  TO  THE  PLANT. 

The  soil  is  that  outer  layer  of  the  earth's  surface  that  serves  as  a 
home  for  plants.  The  harder  part  of  the  soil  underneath  the  culti- 
vated layer  is  called  the  subsoil,  to  distinguish  it  from  the  surface,  or 
true,  soil.  Throughout  a  large  area  of  the  great  valleys  and  plains 
of  California  there  is  no  well  marked  subsoil,  the  characteristics  of 
the  soil  changing  very  little  from  the  surface  downward  for  many 
feet.  This  peculiarity  allows  great  tracts  to  be  graded  for  irrigation 
without  bringing  to  the  surface  a  "raw"  subsoil.  In  humid  regions 
the  surface  soil  is  rarely  more  than  a  few  inches  deep,  and  if  the  sub- 
soil is  brought  to  the  surface  in  more  than  small  amounts  it  is  quite 
detrimental  to  crops  till  it  has  had  time  to  weather  and  become  like 
the  surface  soil. 


15 


Exercise  17. — Soil  and  Subsoil.     (Field  Exercise). 

Apparatus :  Spade. 

Go  to  some  nearby  field  that  has  a  clay  or  clay  loam  soil.  Dig  a 
hole  two  or  three  feet  deep,  carefully  smoothing  one  side  with  a  spade. 
Distinguish  between  the  soil  and  the  subsoil  and  note  the  character- 
istics of  each.  Also  find  a  sandy  soil  and  dig  as  above  described.  Do 
you  find  the  same  marked  division  as  in  the  clay  soil? 

Scientists  tell  us  that  at  one  time  the  surface  of  the  earth  was  en- 
tirely made  up  of  rocks.  Through  many  ages  these  rocks  have  been 
gradually  pulverized  and  powdered  by  many  natural  agencies,  chief 
of  which  are  water,  ice,  heat  and  cold,  and  wind. 

Exercise  18. — Rock  Powder. 

Apparatus :  Hammer  and  anvil  or  heavy  piece  of  flat  iron. 

Get  a  piece  of  clean  rock  material  and  powder  it  with  a  hammer 
on  an  anvil  or  piece  of  iron.  Collect  the  powder  and  compare  it  with 
handfuls  of  different  kinds  of  soils.  How  does  it  differ  from  the 
soils?  Examine  the  rocks  in  the  neighborhood  and  see  if  you  can 
discover  any  evidence  of  their  breaking  down  into  rock  powder. 

But,  as  you  will  have  observed,  rock  powder  differs  from  good 
soil.  We  can  not  grow  a  crop  of  beans,  wheat  or  alfalfa  on  a  soil  made 
up  of  rock  powder.    Devise  an  experiment  to  prove  this. 

Exercise  19. — Plant  Growth  on  Bock  Surfaces.      (Field  Exercise). 

Go  to  some  nearby  place  where  there  are  large  rocks  or  rocky 
cliffs  and  examine  their  surfaces  carefully  to  see  if  you  can  find  any 
plant  growth  on  them.  If  you  search  long  enough  you  will  no  doubt 
find  very  minute  mosses  or  lichens  growing  there.  These  are  able  to 
extract  their  very  small  amount  of  mineral  food  from  the  solid  rock. 

As  the  surface  of  rocks  begins  to  powder,  low  forms  of  plant  life 
find  a  home  upon  them.  After  living  their  simple  life  they  die  and 
their  decaying  bodies  are  mingled  with  the  powdered  rock.  After  a 
time  the  very  poor  soil  formed  in  this  way  is  able  to  support  a  plant 
that  is  a  little  higher  up  in  the  scale  of  life,  and  this  plant  in  its  turn 
adds  its  quota  of  decaying  material  to  the  slowly  forming  soil.  And 
so  the  process  continues  till  the  powder  has  been  changed  to  a  true 
soil  that  is  rich  enough  to  support  the  life  of  the  higher  plants.  Bur- 
rowing animals,  earth  worms  and  insects  have  also  aided  materially 
in  soil  formation,  and  their  bodies  have  added  to  the  decaying  mat- 


16 

ter  supplied  by  the  plants.  This  decaying  organic  matter  which 
mixes  with  rock  powder  to  form  the  true  soil  is  called  humus  and  is 
one  of  the  most  essential  constituents. 

Exercise  20. — Humus  in  Soils. 

Apparatus :  Two  large  test  tubes. 

Place  in  a  large  test  tube  10  c.c.  of  a  10%  solution  of  caustic  soda 
(NaOH)  or  caustic  potash  (KOH)  and  add  about  two  grams  of  a 
dry  rich  soil.  Carefully  heat  to  boiling  and  set  aside  till  the  soil  set- 
tles. Note  the  dark  color  of  the  solution.  The  coloration  is  due  to  the 
humus  in  the  soil  sample.  Repeat  the  test  using  a  very  poor  sandy 
soil.  Note  the  difference  in  the  color  of  the  two  solutions.  With  a 
little  experience  in  its  use,  one  has  in  this  test  a  very  good  index  to 
the  amount  of  humus  in  a  soil. 

Beside  the  rock  powder  and  organic  matter  that  we  have  been 
studying — dead  matter — the  soil  is  full  of  very  active  life.  With  the 
eye  we  can  discover  nothing  more  than  the  parts  that  are  inanimate. 
But  the  high  power  microscope  reveals  an  innumerable  host  of  minute 
organisms  called  bacteria.  They  are  of  many  kinds.  While  some  are 
detrimental,  most  of  them  are  numbered  with  the  farmer's  best 
friends.  We  will  have  occasion  to  mention  some  of  these  in  connec- 
tion with  the  study  of  nitrogen  in  the  soil. 

The  rock  powder,  or  mineral  part  of  the  soil,  is  made  up  of  differ- 
ent sized  particles  and  these  according  to  their  diameters,  are  classi- 
fied from  the  largest  to  the  smallest,  as  sand,  silt  and  clay.  The  value 
of  soils  is  affected  quite  materially  by  a  variation  in  the  amount  of 
these  constituents. 

Exercise  21. — Sand,  Silt  and  Clay  in  Soils. 

Apparatus  :  Balance  and  weights,  mortar,  rubber  pestle,  tall  beaker 
of  about  600  c.c  capacity,  flask  with  a  long,  narrow  neck. 

Weigh  out  about  25  grams  of  an  air  dry  sample  of  loamy  soil,  and 
place  it  in  a  mortar.  Add  about  15  c.c.  water  and  rub  well  with  a 
rubber  pestle.  (This  may  be  made  by  fitting  a  stirring  rod  into  a  one- 
hole  rubber  stopper) .  Let  it  settle  for  a  minute  and  carefully  pour  off 
the  muddy  water  into  a  tall  beaker  of  500  or  600  c.c.  capacity.  Add 
more  water  to  the  mortar  and  repeat  the  operation  till  the  water  in 
the  mortar  no  longer  gets  muddy.  The  part  remaining  in  the  mortar 
is  coarse  sand.  With  small  amounts  of  water  wash  the  sand  from  the 
mortar  through  a  funnel  into  a  flask  with  a  long  neck  (not  over  a 
half  inch  inside  diameter.) 


17 

Add  water  to  the  beaker  containing  the  muddy  material  till  it  is 
nearly  filled.  Stir  thoroughly  and  then  let  it  stand  without  being  dis- 
turbed for  one  hour.  The  muddy  appearance  of  the  water  is  due  to 
the  clay,  which  does  not  settle.  Carefully  siphon  off  the  muddy  water 
without  disturbing  the  sediment.  Fill  the  beaker  again  with  water, 
stir  it,  let  it  settle  for  an  hour  and  siphon  as  before.  Repeat  this  oper- 
ation till  on  standing  an  hour  the  water  above  the  sediment  is  clear, 
showing  the  absence  of  clay.  Transfer  the  sediment  to  the  flask  con- 
taining the  sand.  Nearly  fill  the  flask  with  water  and  stopper  it  well. 
Shake  it  thoroughly  and  invert  it  in  a  funnel  rack  or  ring  stand  so 
that  the  neck  hangs  perpendicular.  Let  the  soil  particles  settle  and 
note  the  different  layers  ranging  from  the  coarse  sand  at  the  bottom 
of  the  neck  to  the  fine  silt  at  the  upper  part.  If  care  is  used  in  weigh- 
ing out  the  sample  this  gives  an  approximately  accurate  way  of  esti- 
mating the  percents  of  sand,  silt  and  clay  in  a  soil.  To  get  the  percent 
of  clay  the  siphoned  clay  water  must  be  made  up  to  a  known  volume 
and  an  aliquot  portion  be  evaporated  to  dryness  and  weighed  in  a 
dish  of  known  weight.  After  this  calculation  is  made  the  remaining 
part  of  100%  is  divided  between  the  sand  and  silt  in  proportion  to  the 
depths  of  each  in  the  flask  neck. 

Rocks  and  Minerals. 

Rocks  are  generally  made  up  of  two  or  more  kinds  of  simpler  sub- 
stances known  as  minerals.  Minerals  are  more  or  less  pure  natural 
chemical  compounds.  A  few  rock  masses  such  as  limestone  and  gypsum 
are  made  up  of  one  kind  of  mineral. 

Soils  are  formed  by  the  breaking  down  of  rocks  into  minerals,  and 
in  some  cases  the  changing  of  the  minerals  by  chemical  action  into 
other  compounds.  Such  a  breaking  down  process  is  called  weathering. 
Below  we  will  discuss  briefly  some  of  the  common  minerals  that  make 
up  the  soil.  For  a  fuller  description  refer  to  a  mineralogy,  or  better, 
to  some  complete  treatise  on  soils,  such  as  that  of  Dr.  Hilgard. 

Quartz,  silicon  dioxide,  is  one  of  the  most  abundant  minerals  and 
hence  is  found  largely  in  soils.  It  contains  no  plant  food  but  is  a 
very  valuable  soil  former  on  account  of  the  effect  it  has  on  the  physical 
properties  of  the  soil.  The  sand  of  humid  regions  is  made  up  almost 
wholly  of  quartz  fragments.  The  sands  of  the  semi-arid  regions  of  the 
West  contain,  besides  quartz,  a  very  high  percentage  of  fragments  of 
other  minerals,  many  of  which  are  rich  in  plant  food.  The  addition 
of  water  and  humus  to  these  arid  sands  renders  much  of  this  food 
easily  available  to  plants,  hence  the  great  richness  of  the  soils  on 


18 

many  of  the  western  plains  recently  opened  to  cultivation  by  the  great 
irrigation  projects  of  the  government. 

Feldspar  is  also  a  very  abundant  mineral.  Weathering  breaks  it  up 
into  clay,  compounds  of  potash  and  lime  which  are  very  valuable  plant 
foods,  and  small  amounts  of  other  substances.  On  account  of  the 
potash  and  clay,  feldspar  is  the  most  valuable  soil  mineral.  There  are 
several  varieties  of  feldspar.  The  one  richest  in  potash  is  called 
orthoclase. 

Mica,  a  somewhat  common,  bright,  scale  like  mineral,  is  often 
called  "isinglass."  Though  it  contains  considerable  potash,  it  is  not 
a  very  valuable  soil  former  because  it  weathers  very  slowly.  The 
bright  shining  particles  in  sand  are  usually  fragments  of  mica. 

Homblend  is  the  name  given  to  a  group  of  dark  colored  minerals 
that  enter  frequently  into  soil  formation.  The  most  common  one  is 
black,  and  as  it  weathers  forms  a  reddish  colored  clayey  soil.  The 
red  color  is  due  to  the  iron  that  the  mineral  contains.  Hornblend 
contains  very  little  plant  food,  but  the  clay  and  iron  that  it  adds  to  the 
soil  aid  materially  in  improving  physical  conditions. 

Serpentine  is  a  greenish  colored  mineral  that  weathers  very  slowly, 
and  contains  little  or  no  plant  food.  It  contains  magnesium,  which 
is  required  in  very  small  quantities  for  plant  growth,  but  the  large 
amount  left  in  the  soil  by  the  weathering  of  this  mineral  and  others 
closely  related  to  it,  is  harmful  to  many  plants.  Large  amounts  of 
lime  in  the  soil  seem  to  overcome  the  evil  effect  of  the  magnesium. 
The  rocks  of  the  California  Coast  range  contain  considerable  serpen- 
tine and  related  minerals.  Talc,  "soapstone, "  is  closely  related  to 
serpentine. 

Limestone  is  carbonate  of  calcium.  It  is  found  in  all  soils  and  is 
not  only  valuable  for  the  plant  food  that  it  contains,  but  has  a  very 
marked  beneficial  effect  on  the  physical  properties  of  the  soil.  When 
it  occurs  in  large  masses  it  is  mined  and  burned  to  produce  the  ' '  lime ' ' 
of  commerce. 

Gypsum  is  a  sulfate  of  calcium.  It  is  even  more  valuable  than 
limestone  as  a  soil  maker.  It  is  slightly  soluble  in  water  and  hence 
is  very  easily  available  to  the  plant.  Besides  its  use  as  a  plant  food 
and  its  good  effect  on  the  physical  condition  of  the  soil,  it  is  used 
extensively  as  a  remedy  for  "black  alkali."  It  is  mined  extensively 
and  ground  and  sold  as  "land  plaster."  When  properly  burned  it  is 
"plaster  paris." 


19 

Apatite  and  Phosphorite  are  minerals  containing  large  amounts  of 
phosphate  of  lime.  This  compound  is  found  in  minute  quantities  in  all 
soils.  Where  these  minerals  are  found  in  large  amounts  they  are 
mined  and  prepared  into  phosphate  fertilizers.  They  are  very  im- 
portant constituents  of  the  soil. 

Exercise  22. — Soil  Minerals. 

Examine  the  minerals  in  the  school  collection  and  learn  which  are 
valuable  soil  formers  and  why.  Search  your  reference  books  to  learn 
what  you  can  of  these  minerals. 

Exercise  23. — Local  Minerals.      (Field  Exercise.) 

Examine  the  rocks  and  minerals  of  the  vicinity.  Make  a  collection 
of  those  that  seem  to  enter  into  the  formation  of  the  soil.  Try  to 
identify  these  minerals  and  then  look  up  their  chemical  composition. 
Does  this  aid  you  in  gaining  a  knowledge  of  the  soils  of  your  locality? 

Alkali. 

The  minerals  thus  far  mentioned  are  all  insoluble  in  water,  or 
nearly  so.  There  is  another  class  that  is  very  readily  soluble.  Many 
of  them  are  formed  by  the  weathering  of  other  minerals.  In  the 
humid  climates  these  soluble  minerals  are  washed  away  in  the  drain- 
age of  the  country.  In  arid  climates  they  remain  in  the  soil  and  are 
called  collectively  "alkali."  The  three  principal  alkali  minerals  are 
sodium  chloride  and  sodium  sulphate,  which  are  known  as  "white 
alkali,"  and  sodium  carbonate,  called  "black  alkali." 

~Etxercise  24. — Alkali. 

Apparatus :  Three  tomato  cans,  three  small  pans,  funnel,  oil  cloth, 
filter  paper,  three  small  evaporating  dishes,  stirring  rod. 

Melt  the  tops  from  the  cans,  being  careful  not  to  cause  them  to 
leak.  Get  enough  clay-loam  soil  to  fill  the  cans  and  divide  it  into 
three  parts.  Put  one  part  untreated  into  the  first  can.  Place  the 
other  two  parts  on  pieces  of  oil  cloth.  To  one  part  add  15  grams  of 
finely  powdered  soda  crystals  (sodium  carbonate,  Na2C03),  mix  thor- 
oughly and  place  in  the  second  can.  To  the  other  portion  add  5  grams 
each  of  common  salt  (sodium  chloride  NaCl)  and  Glauber's  salt 
(sodium  sulphate  Na2S04),  finely  powdered.  Mix  thoroughly  and 
place  in  the  third  can.  Add  enough  water  to  each  can  to  saturate  the 
soil.  When  the  water  has  settled  compact  the  surfaces  of  the  soil  in 
the  cans  so  that  it  is  quite  hard.    Place  the  cans  in  a  warm  place  for 


20 

two  or  three  days  and  watch  for  results.  The  first  can  serves  as  a 
check.  What  difference  in  the  appearance  of  the  surface  of  the  soil 
in  the  three  cans?  Sodium  carbonate,  though  white,  acts  chemically 
with  the  humus  in  the  soil,  forming  a  black  substance  which,  as  the 
water  evaporates,  is  left  on  the  surface  of  the  soil  as  a  dark  colored 
excresence;  hence  the  name,  " black  alkali."  The  chemicals  in  the 
third  can  do  not  act  on  the  humus,  and  hence  come  to  the  surface 
white.  Again  thoroughly  wet  the  soils,  adding  only  a  little  water 
at  a  time  so  that  the  alkali  may  be  washed  down  into  the  soil  as  it  dis- 
solves. Beginning  as  soon  as  the  soils  are  in  condition  to  work,  culti- 
vate the  cans  to  the  depth  of  an  inch  every  day  for  a  week.  Why 
does  not  the  alkali  come  to  the  surface  again? 

Perforate  the  bottoms  of  the  cans  with  a  nail.  Place  each  in  a 
separate  pan  and  add  water  a  little  at  a  time  until  about  a  pint  of 
drain  water  is  collected  from  each  can.  Again  pack  the  soil  surface 
and  place  the  cans  in  a  warm  place  for  two  or  three  days.  Filter 
about  100  c.c.  portions  of  each  of  the  drainage  waters  into  separate 
evaporating  dishes  and  evaporate  to  dryness.  Is  there  as  much  residue 
in  the  first  sample  as  in  the  second  or  third?  With  a  stirring  rod 
taste  the  first  residue.  Add  a  few  drops  of  dilute  hydrochloric  acid 
(HC1)  to  the  second  residue.  An  effervescence  (frothing)  shows  car- 
bonates present.  Try  the  first  residue  in  the  same  way.  Is  the  result 
the  same?  Taste  the  third  residue.  Is  it  salty?  Does  it  taste  like 
the  first?  Have  the  alkalies  been  washed  from  the  soil?  After  the 
cans  have  stood  for  two  or  three  days  again  examine  their  surfaces. 
Do  they  show  alkali  as  before?  Draw  conclusions  from  this  exercise 
as  to  the  nature  of  alkali  and  methods  of  ridding  the  land  of  it. 

Exercise  25. — Gypsum  Treatment  for  Black  Alkali. 

Apparatus  :  A  tomato  can. 

Prepare  a  can  of  the  same  kind  of  soil  as  in  the  last  experiment. 
Weigh  out  15  grams  each  of  soda  crystals  and  gypsum  (land  plaster) T 
powder  each  thoroughly  and  mix  them  with  the  soil  before  placing  it 
in  the  can,  add  water  to  the  soil  slowly  till  it  is  saturated.  Compact 
as  in  the  last  experiment.  Place  in  a  warm  place  for  two  days  and 
note  the  incrustation.  Is  it  "  black  alkali ' '  or  has  the  gypsum  changed 
it?  How  does  the  residue  compare  with  that  in  the  third  can  in  the 
last  experiment?  If  the  materials  have  been  well  mixed  the  sodium 
carbonate  will  have  acted  with  the  calcium  sulphate  (gypsum)  and 
formed  insoluble  calcium  carbonate  (limestone)  and  sodium  sulfate, 
one  of  the  compounds  in  "white  alkali."     In  this  manner  the  very 


21 

harmful  ''black  alkali"  can  be  changed  to  much  less  dangerous  white 
variety. 

Besides  containing  harmful  minerals,  most  alkali  soils  are  rich 
in  soluble  plant  food,  such  as  nitrates  and  potassium  compounds. 
Learn  all  that  you  can  about  the  reclamation  of  alkali  lands.  Consult 
Dr.  Hilgard's  "Soils"  and  the  publications  of  the  California  Experi- 
ment Station,  which  furnish  valuable  references  on  this  subject. 

Exercise  26. — Local  Alkali  Lands.     (Field  Exercise.) 

Visit  the  localities  near  your  school  where  alkali  is  found.  Make 
inquiry  of  the  farmers  to  learn  what  has  been  done  to  better  the  con- 
ditions. Compare  the  efficiency  of  different  methods.  Learn  if  irri- 
gation has  had  any  part  in  causing  the  land  to  become  "alkalied. " 
Write  a  short  article  on  "How  to  improve  Alkali  Lands,"  basing 
your  statements  on  your  observations  and  reading. 

Acid  Soils. 

Not  only  do  we  have  alkali  lands,  but  in  some  localities  may  be 
found  soils  that  are  decidedly  acid.  They  are  commonly  spoken  of 
as  "sour"  soils.  Many  varieties  of  plants  will  not  grow  on  these 
lands,  and  the  beneficial  bacteria,  such  as  the  nitrate  producers,  can- 
not thrive  in  them  till  the  sourness  is  removed. 

The  soils  most  commonly  found  to  be  acid  are :  those  that  are  very 
rich  in  humus  producing  matter,  such  as  boggy  marsh  land  and  tule 
land ;  poorly  drained  clay  soils ;  and  soils  that  have  been  treated  with 
large  amounts  of  acid  producing  fertilizers.  Drainage  will  generally 
remove  the  causes  of  acidity.  Lime  and  wood  ashes  are  the  best 
chemical  remedies  for  sour  soils.  They  improve  it  by  neutralizing  the 
acids.    Acid  soils  are  not  very  common  in  California. 

Exercise  27. — Alkali  and  Acid  Soil  Tests. 

Apparatus :  Three  small  dishes,  red  and  blue  litmus  paper. 

Select  two  or  three  samples  of  soils  from  alkali  spots.  Also  get 
samples  from  boggy  soils  and  from  poorly  drained  heavy  clay  soils. 
Place  small  handfuls  of  each  of  these  samples  in  separate  pans  or 
dishes.  Insert  in  each  sample  small  strips  of  red  and  of  blue  litmus 
paper.  Moisten  with  distilled  water  and  press  the  soils  down  firmly 
about  the  papers.  Let  them  stand  for  an  hour  or  more.  Carefully 
remove  the  papers  from  the  soil,  wash  them  thoroughly  with  distilled 
water  and  dry  them  in  a  room  that  is  free  from  laboratory  gases. 
Examine  them  when  dry  and  compare  their  colors  with  the  original 
paper.  "Black  alkali"  will  turn  the  red  litmus  to  blue,  and  acids 
will  turn  the  blue  to  red. 


22 


HOW  PLANTS  GET  NITBOGEN. 

Nitrogen  is  obtained  by  the  plant  from  compounds  found  in  the 
soil.  Unlike  the  other  elements  that  the  plant  extracts  from  the  soil, 
it  is  not  a  constituent  of  rocks,  and  hence  is  not  produced  for  the  plant 
by  rock  weathering.  It  comes  indirectly  from  the  air.  The  principal 
sources  of  nitrogen  plant  food  are  two.  First,  all  animal  or  vegetable 
matter  contains  more  or  less  of  the  element  combined  with  other  ele- 
ments in  the  formation  of  the  tissues.  As  this  matter  decays  certain 
classes  of  bacteria  act  upon  it  and  along  with  many  other  changes,  the 
nitrogen  is  passed  through  a  series  of  changes  till  it  forms  nitrates 
which  are  easily  available  for  plant  food.  Second,  a  class  of  bacteria 
entirely  independent  of  those  mentioned  in  the  first  part,  make  their 
home  on  the  roots  of  certain  plants  and  are  able  to  change  the  free 
nitrogen  of  the  air  to  nitrates  which  are  used  or  stored  by  the  plant 
on  which  the  bacteria  make  their  home. 

Exercise  28. — Nitrogen  Nodules.     (Field  Exercise.) 

Go  into  the  fields  and  pastures  and  carefully  dig  without  injury 
to  the  roots  (this  may  be  accomplished  more  easily  when  the  soil  is 
quite  wet)  a  specimen  or  two  of  each  of  as  many  of  the  following 
plants  as  you  can  find:  field  pea,  sweet  pea,  field  bean,  soy  bean, 
horse  bean,  lupine,  alfalfa,  burr  clover,  red  clover,  white  clover,  vetch. 
Examine  the  roots  for  very  small  potato-like  knots.  These  plants  all 
belong  to  the  same  botanical  family,  ' '  leguminosae, "  and  are  called 
commonly  legumes.  They  are  distinguished  from  other  plants  by 
their  blossoms,  which  are  all  "butterfly  shaped,"  having  a  keel  and 
wings ;  though  the  blossoms  of  some,  as  the  clovers,  are  so  small  that 
they  hardly  show  the  form  without  being  very  closely  examined.  Ex- 
amine the  roots  of  wheat,  oats,  barley  or  corn  for  knots  like  those 
found  on  the  legumes.    Do  you  find  any? 

The  knots,  or  "nodules"  as  they  are  called,  are  the  home  of  the 
bacteria.  In  some  way  these  minute  organisms  are  able  to  use  the 
free  nitrogen  of  the  soil  air  and  combine  it  with  the  mineral  matter 
of  the  soil  to  form  nitrates.  The  plant  cannot  use  the  free  nitrogen 
but  flourishes  on  the  nitrates,  which  the  bacteria  offer  as  rental  for 
the  home  provided  by  the  legume.  The  plant  satisfies  its  needs  from 
the  nitrates  thus  produced  and  any  excess  remains  in  the  soil  for  a 
future  crop.  This  suggests  a  reason  for  the  crop  rotation  practice  of 
following  a  legume  crop  (a  nitrogen  food  producer)  by  a  cereal  crop 
(a  nitrogen  food  consumer).  Nitrogen  is  by  far  the  most  expensive 
plant  food  to  buy  in  the  form  of  fertilizers,  so  any  cropping  practice 


23 

that  will  add  it  to  the  soil  without  additional  cost  should  be  followed 
by  the  farmer.  Some  leguminous  crop  should  form  a  part  of  every 
system  of  rotation.  Make  a  study  of  the  crops  of  your  locality  and 
see  what  legumes  are  the  best  and  most  profitable  producers. 

CLASSIFICATION  OF  SOILS. 

Soils  are  divided  into  two  classes  according  to  their  location  with 
respect  to  the  rocks  from  which  they  are  derived.  Sedentary  soils  are 
those  that  are  formed  directly  over  the  parent  rock.  They  are  also 
called  residual  soils,  and  ' '  soils  in  place. ' '  They  partake  of  the  char- 
acteristics of  the  underlying  rocks.  Transported  soils  are  those  that 
have  been  moved  some  distance  from  the  rock  that  gave  them  origin. 
They  are  sub-named  according  to  the  method  of  their  removal  from 
the  original  source.  Colluvial  soils  are  formed  by  the  soil  and  dis- 
integrated rock  masses  sliding  and  washing  down  a  hillside  and  lodg- 
ing at  its  base.  Though  changed  slightly  by  washing,  they  partake 
largely  of  the  nature  of  the  rocks  from  which  they  slid.  Alluvial  soils 
are  formed  by  the  deposits  of  streams.  They  form  the  valley  lands, 
and  are  made  up  of  the  materials  gathered  all  along  the  course  of  the 
stream.  They  partake  of  the  characteristics  of  the  rocks  of  the  entire 
drainage  area  from  which  they  are  derived,  but  are  much  modified 
by  the  velocity  of  the  water  and  the  amount  of  weathering  that  has 
taken  place.  Drift  soils  are  those  deposited  by  the  melting  of  glaciers. 
Aeolian  soils  are  those  that  have  been  carried  and  deposited  by  the 
wind. 

Experiment    29. — Classifying    Local    Soils    According    to    Location. 

(Field  Exercise.) 

Sketch  a  map  of  your  locality,  showing  the  different  kinds  of  soil 
formations  according  to  the  above  method  of  naming.  Give  your  rea- 
sons for  so  naming  each  kind.  Dig  into  each  kind  of  soil  and  study  the 
shape  and  nature  of  the  rock  fragments.  Are  there  any  aeolian  or  drift 
soils  in  the  vicinity? 

Exercise  30. — Sampling  Soils.     (Field  Exercise.) 

Apparatus  :     Spade,  pail,  oil-cloth. 

Select  a  spot  for  sampling  and  carefully  remove  from  the  surface 
all  stones,  stubble,  and  other  matter  not  belonging  to  the  soil.  Dig 
into  the  cleared  space  a  V-shaped  hole  with  one  side  of  the  V  perpen- 
dicular, and  a  little  wider  than  the  spade.  On  the  perpendicular  side, 
measure  the  depth  to  the  change  in  color,  which  indicates  the  division 


24 

between  the  soil  and  subsoil.  Carefully  clear  out  all  the  loose  soil 
from  the  hole.  With  the  spade  shave  thin  slices  from  the  perpendicu- 
lar side,  collecting  the  soil  in  a  pail  till  you  have  about  a  quart  of  the 
sample.  In  the  same  manner  take  samples  of  like  amount  from  other 
parts  of  the  field,  placing  them  in  the  same  pail  as  the  first.  Pour  all 
the  soil  thus  collected  onto  a  piece  of  oil-cloth  and  mix  it  thoroughly. 
Save  about  a  half  gallon  of  the  mixture  for  the  sample  of  the  field. 
If  there  are  two  or  more  distinct  kinds  of  soil  in  a  field,  sample  each 
of  them  and  keep  the  samples  separate.  If  there  is  no  marked  line 
between  the  soil  and  the  subsoil,  sample  to  the  depth  of  one  foot.  The 
subsoil  may  be  sampled  in  the  same  manner  as  the  surface  soil.  Care 
must  be  taken  to  remove  all  loose  soil  from  the  hole  before  commencing 
to  collect  the  subsoil  sample. 

Soils  may  be  sampled  to  a  greater  depth  with  an  old  wood  augur 
that  cuts  about  a  two-inch  hole.  Have  the  blacksmith  fasten  a  half 
inch  pipe  coupling  to  the  head  of  the  bit.  Cut  and  thread  three  pieces 
of  pipe  each  about  eighteen  inches  long,  for  extensions  to  the  shank 
of  the  augur.  Use  a  half -inch  "tee"  with  a  piece  of  pipe  about  a 
foot  long  screwed  into  each  side,  for  a  handle.  In  sampling  the  soil, 
draw  the  augur  at  each  foot  in  depth  and  place  the  borings  in  separate 
cans  or  pails. 

Soil  Moisture, 

On  a  previous  page  it  was  mentioned  that  the  soil  was  made  up  of 
rock  powder  and  humus,  and  that  it  contained  a  multitude  of  living 
organisms,  bacteria.  The  soil  also  contains  air  and  water,  and  its 
value  as  a  crop  producer  is  materially  effected  by  the  relative  amounts 
of  these  two  constituents. 

Exercise  31. — Moisture  in  the  Soil. 

Apparatus :  Spade,  oil-cloth,  screw-top  jar,  balance  and  weights, 
oven  and  thermometer,  small  weighing  pan. 

Collect  a  sample  of  soil  as  directed  under  the  sampling  of  soils. 
Cover  it  at  once  to  prevent  any  evaporation.  Carry  to  the  laboratory 
and  weigh  the  sample  as  soon  as  possible.  Carefully  spread  it  on  a 
piece  of  oil  cloth  and  place  it  in  a  dry  room  where  it  will  not  be  dis- 
turbed. After  two  or  three  days  weigh  the  sample,  expose  to  the  air 
again  and  the  next  day  weigh  the  sample  again.  Continue  this  until 
there  is  no  longer  a  loss  in  weight.  Record  the  total  loss  and  calculate 
the  percent  of  moisture  lost.  But  this  is  not  all  the  water  that  the 
soil  contains.  Each  particle  is  yet  covered  with  a  very  thin  film, 
called  "hygroscopic  moisture" — the  part  that  cannot  evaporate  at  the 


25 

ordinary  temperature.  The  soil  is  now  said  to  be  "air-dry."  De- 
termine the  percent  of  hygroscopic  moisture  in  the  air  dry  sample 
obtained,  by  the  same  method  that  you  determined  the  moisture  in  the 
plant,  Exercise  1,  using  a  temperature  from  100°  to  105°  C. 

Exercise  32. — Collecting  Local  Soils.     (Field  Exercise.) 

Apparatus:  Spade,  collecting  pails,  bottles  or  jars  for  preserving 
samples. 

Collect  samples  of  soil  from  the  neighborhood,  getting  as  many 
varieties  as  possible,  from  coarse  sandy  soils  at  one  extreme  to  heavy 
clay  soils  at  the  other.  Spread  the  samples  on  old  newspapers  in  a 
dry  place  till  they  air-dry,  then  set  them  away  in  wide  mouth  bottles 
or  jars,  properly  labeled  as  to  locality,  and  save  them  for  future  use. 

Exercise  33. — Water  Holding  Capacity  of  the  Soil. 

Apparatus :  Balance  and  weights,  three  funnels,  niters,  50  c.c. 
graduated  cylinder. 

Use  three  funnels  of  a  diameter  of  about  four  inches.  Fit  a  filter 
to  each  funnel  and  moisten  each  with  water  and  let  drain  till  water 
no  longer  drips  from  the  funnel.  Weigh  out  50  gram  samples  each  of 
air-dry  heavy  clay,  loamy,  and  coarse  sandy  soils.  Place  the  weighed 
samples  each  in  one  of  the  prepared  funnels.  Place  a  beaker  under 
each  funnel.  Add  slowly  to  each,  50  c.c.  water  and  let  them  drain 
till  water  no  longer  drips  from  the  funnels.  Measure  the  number  of 
cubic  centimeters  of  water  that  drains  from  each  sample.  Subtract 
these  amounts  from  the  50  c.c.  used  and  the  difference  will  be  the 
water  absorbed  by  the  sample.  As  a  cubic  centimeter  of  water 
weighs  a  gram,  the  c.c.s  absorbed  multiplied  by  2  will  give  the  grams 
of  water  absorbed  by  100  grams  of  soil,  or  the  water  holding  capacity 
expressed  in  percent.  How  do  the  results  compare  for  the  three  kinds 
of  soil  used. 

Exercise    34. — The   Effect   of   Organic   Matter   on    Water   Holding 

Capacity. 

Apparatus :  Balance  and  weights,  funnel,  filter,  graduated  cylinder. 

Mix  together  thoroughly  40  grams  of  air-dry  coarse  sandy  soil  and 
ten  grams  of  fine  air-dry  leaf  mold  or  well  rotted  stable  manure.  In 
the  same  way  prepare  a  sample  of  the  air-dry  heavy  clay  loam,  40 
grams,  and  10  grams  of  the  manure  or  leaf  mold.  Determine  the 
water  holding  capacity  of  these  prepared  samples  as  you  did  the  soils 


26 

in  the  last  exercise.  Tabulate  the  results  of  the  two  exercises  and 
draw  your  conclusions  as  to  the  effect  of  manures  on  the  power  of  a 
soil  to  absorb  moisture. 

Exercise  35. — Size  of  Particles  and  Water  Holding  Capacity. 

Apparatus :  Balance  and  weights,  hammer. 

Weigh  accurately  a  large  smooth  pebble  about  one  and  one-half 
inches  in  diameter.  Dip  it  into  water,  remove  it  and  immediately 
weigh  again.  Calculate  the  ratio  of  the  weight  of  the  adhering  water 
to  that  of  the  pebble.  Dry  the  pebble  and  with  a  hammer  carefully 
break  it  into  five  or  six  good  sized  pieces.  Weigh  these  pieces  that 
any  loss  of  small  particles  may  be  accounted  for,  and  dip  each  into 
water  and  remove  and  weigh  as  above.  Calculate  the  ratio  of  the 
weight  of  the  total  amount  of  water  adhering  to  pieces  to  that  of  the 
combined  weight  of  the  pieces.  How  does  this  ratio  compare  with  the 
first  one?  The  surface  in  the  second  case  has  been  increased  by  the 
total  amount  of  broken  area,  which  is  added  to  the  area  of  the  un- 
broken pebble.  Diminishing  the  size  of  the  particles  in  a  given  weight 
of  soil,  then,  increases  the  surface.  Which  has  the  greater  water  hold- 
ing capacity  in  proportion  to  weight,  a  coarse  soil  or  a  fine  one?  Is 
this  conclusion  born  out  by  your  experience  with  sandy  and  clay  soils 
in  the  previous  exercises? 

Exercise  36. — Capillarity. 

Apparatus :  Two  wide  mouth  bottles,  250  c.c,  2  wide  mouth  bottles, 
60  c.c,  balance  and  weights,  lamp  wick. 

Use  two  wide  mouth  bottles  of  equal  size,  capacity  about  250  c.c. 
Place  the  bottles  side  by  side  and  fill  one  of  them  two-thirds  full  of 
water.  Thoroughly  wet  a  lamp  wick  and  place  it  so  that  one  end  dips 
about  an  inch  into  water  and  the  other  end  hangs  in  the  empty  bottle. 
Let  it  stand  for  about  an  hour.  Make  a  drawing  of  the  apparatus. 
The  water  rises  through  the  wick  by  the  process  known  as  "capillar- 
ity. ' '    What  causes  the  oil  to  rise  in  the  wick  of  a  kerosene  lamp  ? 

Into  a  small  wide  mouth  bottle  (60  c.c.)  pour  kerosene  till  it 
stands  about  three-fourths  of  an  inch  deep.  Fill  the  bottle  with  finely 
powdered  air-dry  soil,  and  press  down  the  surface  with  the  fingers. 
Let  it  stand  for  about  15  minutes.  Does  the  kerosene  rise  through 
the  soil?  Apply  a  lighted  match  to  the  surface  of  the  soil.  Explain 
what  has  taken  place. 

Repeat  the  second  part  of  the  experiment,  using  water  instead  of 


27 

the  kerosene.  After  the  moisture  reaches  the  surface  weigh  the  bottle 
and  set  it  away  in  a  warm  place  until  the  next  laboratory  period. 
Weigh  the  bottle  again.     Explain  any  change  in  weight. 

Exercise  37. — Soil  Capillarity. 

Apparatus :  Granite  ware  pan,  capillary  tubes. 

(a)  Use  a  granite  ware  pan  about  10  by  12  inches  in  size,  or  an 
ordinary  tin  milk  pan  may  be  used.  Pour  good  loamy  soil,  air-dry, 
into  the  middle  of  the  pan  till  a  sharp  mound  stands  several  inches 
high,  without  rising  on  the  sides  of  the  pan.  Carefully  pour  water 
around  the  inside  edge  of  the  pan  till  it  stands  nearly  two  inches  deep. 
Watch  the  mound  of  soil  and  explain  what  takes  place.  Does  this 
show  in  any  way  how  the  higher  parts  of  a  field  may  get  water  for 
plant  growth  ?  Why  is  it  that  some  creek  and  river  bottom  lands  grow 
excellent  crops  of  alfalfa  without  irrigation? 

( o )  Place  the  ends  of  several  sizes  of  capillary  tubing  into  a  bottle 
of  water  colored  with  ink.  How  does  the  rise  of  the  water  in  the  tubes 
relate  to  their  diameters?  The  soil  is  full  of  very  minute,  though 
very  crooked  tubes.  They  are  formed  by  the  spaces  between  the  soil 
particles,  and  it  is  through  these  tube-like  spaces  that  the  water  rises. 

Exercise  38. — Porosity  of  Soil. 

Apparatus :  Graduate  cylinder,  wide  mouth  bottle  250  c.c,  a  stiff 
wire. 

Measure  the  water,  to  the  nearest  cubic  centimeter,  necessary  to 
fill  a  wide  mouth  bottle,  of  about  250  c.c.  capacity,  to  the  neck.  Pill 
the  bottle  to  the  neck  with  an  air-dry  sandy  soil.  From  a  vessel  con- 
taining a  measured  quantity  of  water,  pour  slowly  into  the  bottle.  Stir 
the  soil  gently  with  a  stiff  wire,  if  necessary,  to  allow  the  water  to 
penetrate  to  the  bottom  and  the  air  to  escape.  When  the  soil  is  thor- 
oughly saturated  with  water  to  the  neck  of  the  bottle,  measure  the 
amount  remaining  in  the  vessel.  The  amount  of  water  used  to  satu- 
rate the  soil  equals  the  volume  of  pore  space  that  it  contains.  Volume 
of  water  used  divided  by  the  volume  of  the  soil  and  multiplied  by  100 
will  give  the  porosity  expressed  in  percent  of  the  volume. 

Under  natural  conditions  in  the  field  the  pore  space  is  filled  partly 
with  air  and  partly  with  water.  With  ordinary  soils  the  condition  best 
suited  to  crop  growth  is  when  the  pore  space  is  about  half  filled  with 
air  and  half  with  water. 


28 


Exercise  39. — Shrinkage  of  Clays. 

Apparatus :  Three  can  lids,  a  small  pan  for  mixing  soils. 

Mix  a  handful  of  clay  soil  with  a  little  water  and  mix  into  a  stiff 
dough,  being  careful  to  have  it  thoroughly  wetted  all  the  way  through. 
Make  a  similar  dough  of  the  clay  soil  mixed  with  about  one-third  as 
much  leaf  mold  or  other  well  rotted  organic  matter.  Prepare  a  third 
sample  from  a  sandy  soil.  Pack  each  of  these  samples  into  a  small  bak- 
ing powder  can  lid,  or  similar  container,  and  set  them  away  in  a  warm 
dry  place  till  the  next  laboratory  period  and  then  examine  them  for 
shrinkage  and  cracks.  What  do  you  find  ?  Do  you  find  similar  results 
in  the  fields  after  a  period  of  dry  weather? 

Exercise   40. — The  Effect   of   Color  on  Soil   Temperature.      (Field 

Exercise.) 

Apparatus  :  Two  thermometers,  hoe,  ruler. 

Select  a  smooth,  open  space  in  the  field,  away  from  any  shade. 
The  day  must  be  warm  and  sunny.  Clear  the  surface  of  the  soil  of 
any  stubble  or  rubbish  for  a  space  about  four  feet  square.  Within 
this  cleared  space  lay  off  two  eighteen-inch  circles  and  cover  one  to 
the  depth  of  about  14  inch  with  lamp  black,  and  the  other  to  the  same 
depth  with  whiting  or  other  powdered  white  material.  Insert  the  bulb 
of  a  thermometer  into  the  soil  in  the  center  of  each  circle  to  the  depth 
of  an  inch.  Examine  and  record  the  temperature  of  each  every  five 
minutes  for  at  least  half  an  hour,  or  until  there  is  a  decided  difference. 
What  effect  does  color  seem  to  have  on  the  temperature  of  the  soil, 
other  conditions  remaining  the  same? 

Exercise  41. — The  Effect  of  Evaporation  on  Soil  Temperature. 

Apparatus :  Four  tomato  cans,  4  thermometers,  plotting  paper. 

Fill  two  tomato  cans  with  air-dry  clay  soil  and  two  with  air-dry 
sandy  soil.  Moisten  well  one  can  each  of  the  clay  soil  and  the  sandy 
soil.  Bury  the  four  cans  side  by  side  in  dry  soil  in  a  sunny  spot  in 
the  field,  leaving  about  half  an  inch  of  the  tops  above  the  surface.  In- 
sert a  thermometer  in  each  to  the  depth  of  an  inch,  and  read  and  re- 
cord the  temperature  about  every  hour  throughout  the  day,  noting 
the  time  of  each  reading.  On  plotting  paper  draw  a  curve  of  tempera- 
tures for  each  can,  using  Time  and  Temperature  for  the  co-ordinates. 
Use  different  colored  inks  or  pencils  to  represent  the  curves  of  the 
four  samples.    If  the  first  day  of  the  experiment  does  not  show  decided 


29 

results  continue  the  readings  through  the  second  day.  What  is  your 
conclusion  as  to  the  effect  of  evaporation  on  soil  temperature?  Which 
shows  the  greater  changes,  the  moist  clay  or  the  moist  sand?     Why? 

Exercise  42. — Effect  of  Mulches  and  Cultivation   on  Evaporation. 

(Field  Exercise.) 

Apparatus:  Described  in  body  of  the  exercise. 

Remove  the  tops  from  eight  good  five-gallon  coal  oil  cans,  by  cut- 
ting around  the  top  just  inside  the  rim.  Hammer  the  ragged  edge 
down  smoothly  against  the  sides  of  the  can.  Fill  each  to  the  depth  of 
an  inch  with  fine  gravel.  Place  in  a  corner  of  each  can  a  piece  of 
half-inch  water  pipe  long  enough  to  reach  to  just  above  the  edge  of 
the  can.  Fill  the  cans  all  alike  with  soil  to  within  two  inches  of  the 
tops,  gently  jolting  the  cans  on  the  ground  as  you  fill  them  to  compact 
the  soil.  Number  the  cans  from  one  to  eight.  Cover  the  soil  in  number 
six  with  a  mulch  of  one  inch  of  coarse  sand.  Cover  number  seven 
with  a  mulch  of  an  inch  of  finely  cut  dry  straw.  Cover  number  eight 
with  a  mulch  of  an  inch  of  fine  stable  manure.  Weigh  each  can  and 
record  the  weights.  Select  an  open  place  in  a  lot  or  field  that  will  be 
free  from  disturbance  and  bury  the  cans  in  the  ground  till  the  sur- 
faces inside  and  out  are  on  the  same  level.  Place  them  in  a  row  about 
two  feet  apart,  arranging  them  according  to  their  numbers.  Pour 
through  a  funnel  a  measured  quantity  of  water  into  the  pipe  in  each 
can,  adding  it  slowly  so  that  the  soil  will  have  plenty  of  time  to  take 
it  up.  Keep  adding  the  water  till  the  cans  without  a  mulch  begin  to 
show  a  little  dampness  at  the  top.  Make  the  quantity  the  same  added 
to  each  can.  During  the  experiment  leave  the  surfaces  of  numbers 
1,  6,  7,  and  8  undisturbed.  Cultivate  the  others  carefully  once  each 
week  with  a  small  garden  tool,  or  a  sharp  stick,  as  follows : 

Number  two,  one  inch  deep. 

Number  three,  two  inches  deep. 

Number  four,  three  inches  deep. 

Number  five,  four  inches  deep. 

Continue  the  experiment  for  from  six  to  ten  weeks,  adding  meas- 
ured quantities  of  water  to  the  cans  as  they  need  it  to  keep  them  in 
good  condition  for  crop  growth.  Keep  a  record  of  the  amount  of 
water  added  to  each  can.  After  there  seems  to  be  a  considerable 
difference  in  the  amounts  of  water  taken  up  by  the  soils  in  the  various 
cans,  carefully  dig  them  up  and  remove  the  soil  adhering  to  the  out- 
sides  of  the  cans.  Wipe  each  can  clean  with  a  cloth  and  weigh  and 
record  the  weight.    Add  to  the  original  weight  of  each  can  of  soil  the 


30 

weight  of  the  water  added  to  it,  and  subtract  from  the  result  the  last 
weight  of  the  can.  The  difference  represents  the  weight  of  water 
evaporated.  Any  rainfall  during  the  time  of  the  experiment  must  be 
taken  into  account  in  making  the  above  calculations.  Tabulate  your 
results  and  draw  conclusions  as  to  the  effectiveness  of  the  mulches 
and  the  different  depths  of  cultivation  in  retaining  the  moisture  in 
soils. 

Exercise  43. — Windbreaks  and  Soil  Moisture.  (Field  Exercise.) 
Apparatus:  Same  as  for  soil  sampling  and  determining  moisture. 
Select  a  good  size  field  that  is  protected  by  a  wind  break  of  trees. 
The  conditions  of  soil,  cultivation  and  cropping  should  be  the  same 
over  the  part  of  the  field  studied.  On  the  side  from  which  the  prevail- 
ing wind  blows,  with  a  soil  augur  take  first  and  second  foot  samples 
at  thirty  feet  from  the  hedge,  and  at  every  100  feet  from  there  out 
till  you  have  sampled  five  or  more  places.  Seal  and  label  the  samples 
obtained  and  take  them  to  the  laboratory  and  determine  the  percent  of 
moisture  in  each  sample  by  the  method  used  in  exercise  30.  What  are 
your  conclusions  as  to  the  effect  of  windbreaks  in  retaining  soil 
moisture? 

Fertilizers. 

Exercise  44. — Fertilizers.     (Field  Exercise.) 

Let  the  students  collect  small  samples  of  the  various  fertilizers 
used  in  the  locality,  procuring  if  possible  from  the  farmers  the  guar- 
antee label  that  goes  with  each  fertilizer.  Make  a  study  of  each  sample 
and  describe  it.  Test  each  with  litmus  paper  and  try  to  determine 
what  causes  the  acidity  or  alkalinity  of  the  samples  that  show  a  test. 

Exercise  £5. — The  Absorption  of  Manure  by  the  Soil. 

Apparatus :  A  pan,  a  tall  quart  can,  a  large  funnel,  a  beaker. 

Soak  a  quart  of  well  rotted  stable  manure  for  two  days  in  enough 
water  to  cover  it.  Perforate  the  bottom  of  a  tall  narrow  can,  holding 
about  a  quart,  and  fill  it  with  dry  soil.  Set  it  in  a  large  funnel.  Pour 
off  the  water  from  the  manure  and  note  its  color.  A  large  part  of  the 
fertilizing  value  of  the  manure  has  dissolved  in  the  water.  This  sug- 
gests that  the  practice  of  piling  manure  in  heaps  and  letting  it  lay 
exposed  to  the  leaching  action  of  the  winter  rains  is  a  very  wasteful 
one.  Slowly  pour  the  manure  water  over  the  soil  and  let  it  drain 
through  into  a  beaker.     Compare  the  color  of  the  drainage  with  that 


31 

before  adding  it  to  the  soil.  Has  the  soil  absorbed  the  valuable  part  of 
the  manure?  A  common  practice  is  to  pile  a  load  of  manure  in  a 
place,  throughout  the  field,  and  scatter  the  piles  after  they  have  rotted 
all  winter.  Will  this  give  an  even  distribution  of  the  fertilizing  part 
of  the  manure  ?  Make  a  study  of  the  best  methods  of  saving  and  using 
barnyard  manures.  Make  an  inspection  of  the  farms  in  the  neighbor- 
hood and  see  if  these  methods  are  being  used.  The  teacher  will  be  able 
to  give  references  to  bulletins  and  other  literature  on  the  subject. 

Exercise  46. — Fertilizer  Field  Tests. 

This  set  of  tests  should  be  carried  on  in  cooperation  with  some  pro- 
gressive farmer  whose  farm  is  near  the  school.  Select  a  field  that  is 
not  yielding  well.  The  part  used  should  be  level,  of  a  uniform  texture 
and  thoroughly  tilled  in  preparation  for  the  seed.  Lay  off  a  square  of 
150  feet  on  a  side,  and  measure  in  4%  feet  from  the  outside  all  around 
for  a  walk.  Running  one  way  through  the  middle  lay  off  a  nine- 
foot  walk,  and  perpendicular  to  this  on  each  side  lay  off  four  plats 
each  thirty-three  feet  wide,  with  three-foot  walks  between  them.  This 
gives  eight  plats  each  33  by  66  feet,  and  containing  one-twentieth  of 
an  acre,  each  surrounded  by  a  walk.  Draw  a  diagram  of  these  plats 
in  your  note  book.  A  scale  of  one  centimeter  to  ten  feet  is  a  very  con- 
venient one  for  this  drawing.  When  the  soil  is  thoroughly  prepared, 
and  just  before  seeding,  apply  the  fertilizers  by  sowing  them  broad- 
cast, being  careful  that  all  parts  of  the  plat  receive  the  same  quantity 
of  fertilizers.  The  eight  plats  should  be  fertilized  as  follows :  (Use 
only  high  grade  fertilizers.) 

No.  1.  No  fertilizer,  serving  as  a  check. 

No.  2.  10  lbs.  sulfate  of  potash. 

No.  3.  20  lbs.  acid  phosphate.  t 

No.  4.  10  lbs.  nitrate  of  soda. 

No.  5.  10  lbs.  nitrate  of  soda,  20  lbs.  acid  phosphate. 

No.  6.  10  lbs.  nitrate  of  soda,  10  lbs.  sulfate  of  potash. 

No.  7.  10  lbs.  sulfate  of  potash,  20  lbs.  acid  phosphate. 

No.  8.  10  lbs.  nitrate  of  soda,  10  lbs.  sulfate  of  potash,  20  lbs.  acid 
phosphate. 

Sow  all  the  plats  exactly  alike  with  the  same  kind  of  seed.  One 
of  the  crops  ordinarily  raised  in  the  community,  such  as  corn,  wheat, 
barley,  etc.,  should  be  used.  If  the  class  is  large  enough  three  or  four 
sets  of  plats  as  described  above  may  be  used,  each  being  sowed  to  a 
different  crop.  The  walks  should  be  kept  free  from  weeds  and  grain 
at  all  times.     When  the  crop  is  ripe,  each  plat  should  be  separately 


32 

cut  and  threshed  and  the  yield  of  grain  and  straw  both  carefully 
weighed.  A  study  of  the  yields  of  the  plats  as  compared  with  the  fer- 
tilizers applied  will  give  the  necessary  data  to  determine  what  com- 
bination of  fertilizing  material  will  cause  the  field  to  increase  its  yield 
of  that  particular  crop,  and  will  give  a  partial  check  on  the  defi- 
ciency of  the  soil  in  any  particular  plant  food.  A  second  year  of  tests 
on  the  same  plats  will  serve  as  a  valuable  check  on  the  first  year's 
results. 

Exercise  47. — Manure  and  Gypsum  Field  Tests. 

If  the  instructor  so  desires,  plats  9  and  10  may  be  added  to  the 
eight  used  in  Exercise  46,  and  treated  as  follows : 

No.  9.  20  lbs.  land  plaster  (gypsum). 

No.  10.  A  half  ton  of  stable  manure. 

The  plaster  and  manure  should  be  well  mixed  with  the  soil  and  the 
plats  sown  and  harvested  as  the  others  are.  They  will  probably  show 
more  marked  results  the  second  year  than  the  first. 

Exercise  48. — Orchard  Fertilizer  Tests. 

After  making  a  careful  study  of  exercise  46,  let  the  student  devise 
a  series  of  tests  to  show  the  fertilizer  requirements  of  the  fruit  trees 
in  some  nearby  orchard.  Fertilizers  should  not  be  applied  around 
the  base  of  the  tree  or  much  injury  may  be  done.  The  feeding  roots 
are  spread  over  an  area  equal  to  or  greater  than  that  covered  by  the 
branches,  and  the  fertilizer  should  be  spread  accordingly.  The  trees 
should  be  numbered  and  the  results  noted  for  two  or  three  years.  The 
fertilizers  have  little  apparent  effect  on  the  trees  for  the  first  year. 

Exercise  49. — Crop  Rotation. 

From  the  reference  books  and  bulletins  at  your  command  make  a 
careful  study  of  Crop  Rotation.  Determine  what  the  principal  objects 
of  rotation  are,  and  how  it  is  applicable  to  your  locality.  Visit  the 
most  progressive  farmers  and  learn  their  system  of  crop  rotations. 
"What  are  the  crops  in  each  rotation?  How  are  they  placed,  and  for 
what  reasons  ?  After  making  the  above  studies,  visit  some  farm  where 
rotation  is  not  practiced.  Make  a  map  of  the  farm  and  divide  it  into 
fields  suitable  for  rotation  practice.  Plan  a  system  of  crops  for  the 
farm  as  you  have  mapped  it.  Give  your  reason  for  placing  each  crop 
in  its  place  in  the  system. 


33 


Exercise  50. — Weeds.     (Field  Exercise.) 

Visit  the  farms  in  the  neighborhood  and  inquire  about  the  weeds 
that  are  giving  trouble.  Learn  what  is  being  done  to  destroy  them. 
Make  a  collection  of  all  the  kinds  of  weeds  that  are  proving  to  be 
pests,  and  learn  their  local  names.  Try  to  give  to  each  its  botanical 
name.  (This  will  prove  an  excellent  practice  for  a  class  in  Botany). 
Examine  the  roots,  seeds  and  other  parts  of  each  kind  of  weed.  Draw 
conclusions  from  your  observations  and  state  why  each  is  a  pest.  From 
your  reference  books  learn  all  you  can  about  the  destruction  of  weeds. 

BEFEBENCE  BOOKS. 

The  number  of  excellent  text  books  dealing  with  Elementary  Agri- 
culture is  increasing  rapidly,  so  that  it  is  possible  for  a  school  to  have 
quite  a  complete  library  for  agricultural  reference,  and  the  cost  need 
not  be  great.  The  following  will  prove  especially  helpful  as  refer- 
ences in  this  series  of  exercises : 

1.  The  Soil,  C.  W.  Burkett. 

2.  Principles  of  Soil  Management,  Lyon  and  Fippin. 

3.  Soils,  E.  W.  Hilgard. 

4.  First  Principles  of  Soil  Fertility,  Vivian. 

5.  The  Fertility  of  the  Land,  I.  P.  Roberts. 

6.  Fertilizers,  E.  B.  Voorhees. 

7.  Principles  of  Agriculture,  L.  H.  Bailey. 

8.  Agriculture  for  Schools  of  the  Pacific  Slope,  Hilgard  and  Os- 
terhout. 

9.  Elements  of  Agriculture,  G.  F.  Warren. 

10.  Practical  Agriculture,  J.  W.  Wilkinson. 

11.  One  Hundred  Experiments  in  Elementary  Agriculture,  R.  0. 
Johnson. 

12.  The  Physics  of  Agriculture,  F.  H.  King. 

For  a  first-class  reference  library  covering  the  general  subject  of 
agriculture  every  school  should  have,  if  possible: 

13.  The  Cyclopedia  of  American  Agriculture  (4  vols.),  L.  H. 
Bailey. 

Numbers  1  and  4  are  published  by  the  Orange- Judd  Co.,  New 
York. 

Numbers  2,  3,  5,  6,  7,  8,  9,  12  and  13  are  published  by  The  Mac- 
millan  Company,  New  York. 


34 

Number  10  is  published  by  the  American  Book  Co.,  New  York. 

Number  11  is  published  by  the  author,  R.  0.  Johnson,  Chico,  Cal. 

The  bulletins  and  publications  of  the  California  Experiment  Sta- 
tion, Berkeley,  and  the  Farmers'  Bulletins  of  the  U.  S.  Department 
of  Agriculture  furnish  excellent  references. 

APPARATUS. 

Most  teachers  prefer  to  select  their  own  apparatus  and  adapt  it  to 
the  experiments  to  be  performed.  The  following  list  is  only  sug- 
gestive In  most  of  the  exercises  two  or  more  can  work  together  and 
the  teacher  will  probably  find  it  convenient  to  have  different  sets  of 
students  working  on  different  exercises.  This  will  allow  a  wide  range 
of  work  with  a  small  amount  of  apparatus. 

FOR   THE   SCHOOL. 

One  measuring  tape,  25  feet ;  1  sheet  iron  drying  oven  with  means 
of  heating  it  to  a  temperature  a  little  above  the  boiling  point  of 
water ;  a  collection  of  farm  and  garden  seeds. 

FOR    EACH    TEN    STUDENTS    IN    CLASS: 

One  spade ;  1  hammer ;  2  hoes ;  2  rakes ;  5  garden  trowels ;  2  water- 
ing pots;  5-yard  sticks  (preferably  graduated  in  inches  on  one  side 
and  centimeters  on  the  other)  ;  2  pieces  of  oil-cloth,  2  ft.  square;  5 
pails  for  soil  sampling  (5-lb.  and  10-lb.  lard  pails  with  covers  are  very 
convenient)  ;  10  baking  powder  can  lids  (3  or  4  inches  across  by  1 
inch  deep)  ;  10  pie  pans  (granite  ware  preferable,  or  large  saucers,  or 
soup  plates,  will  do)  ;  5  pans,  quart;  1  dozen  each  half -gallon,  quart 
and  pint  screw  top  fruit  jars;  2  pans,  about  10  by  12  inches  (granite 
ware  preferred)  ;  20  or  30  tomato  cans;  2  long  neck  glass  flasks,  capac- 
ity 500  or  600  c.c,  with  neck  about  five  inches  long  and  about  %  inch 
inside  diameter  (Benningsen's  silt  flask  preferred)  ;  10  kerosene  cans, 
5  gallon;  1  box  adhesive  labels  (Dennison's  207  very  convenient)  ;  2 
dozen  each  of  wide  mouth  bottles,  capacities  approximately  250  c.c, 
125  c.c,  and  60  c.c  (8-oz.,  4-oz.,  and  2-oz.). 

The  following  may  usually  be  used  in  connection  with  the  chemical 
and  physical  laboratories  of  the  schools : 

One  balance,  sensitive  to  1  cgm. ;  1  set  of  weights,  100  gms.  to  1 
cgm. ;  12  erlenmeyer  flasks,  250  c.c. ;  12  tall  beakers,  500  c.c. ;  12  porce- 
lain crucibles,  no.  0 ;  5  graduated  cylinders,  100  c.c ;  2  packages  filters, 
5-in. ;   12   evaporating  dishes,   diam.   2y2  in. ;   12   glass  funnels,   3  in. 


35 

diam.,  short  stems ;  4  doz.  test  tubes,  5  in.  by  %  in. ;  2  doz.  test  tubes,  7 
in.  by  1  in. ;  6  hard  glass  test  tubes,  6  in.  by  %  in. ;  6  rubber  stoppers, 
one  hole,  to  fit  hard  glass  tubes;  1  thermometer,  0  to  200°  C. ;  4  ther- 
mometers, 0  to  212°  F. ;  1  porcelain  mortar,  3  in.  (a  heavy  coffee  cup 
will  do.) 

CHEMICALS. 

For  the  exercises  where  chemical  tests  are  made  the  following 
chemicals  will  be  needed : 

One  pound  each  of  concentrated  hydrochloric  and  nitric  acids 
and  ammonia ;  100  c.c.  of  each  of  the  following  test  solutions  of  the 
strength  usually  used  in  chemical  laboratories:  potassium  sulpho- 
cyanate,  ammonium  oxalate,  silver  nitrate,  barium  chloride,  sodium 
phosphate,  ammonium  molybdate;  sodium  hydroxide,  iodine;  y» 
pound  each  of  crystals  of  sodium  carbonate,  sodium  sulphate,  sodium 
chloride  (common  salt),  soda-lime;  1  pint  of  ether;  1  pint  of  kero- 
sene ;  fertilizers  sufficient  for  the  fertilizer  experiments. 


